Various organic-base paints for painting metals are well known to the art and their deficiencies as protective coatings for metals are likewise well-recognized. Numerous inorganic-base protective coatings have been devised, each of which relies upon a somewhat different mechanism for efficiency and protection. Of the various inorganic-base coatings developed, those utilizing the alkali metal silicates are probably the most useful. In general, these alkali metal silicate coatings have contained reactive solid powdered ingredients such as zinc powder, aluminium powder, ZnO, Al.sub.2 O.sub.3, or TiO.sub.2. The metallic particles behave an sacrificial anodes with the alkali metal silicate comprising a binder or matrix therefor. In both types of coatings, the mixture must be undertaken essentially immediately before the coating is to be applied since the shelf life thereof is short. Moreover, the mixing process can be hazardous to health, especially in the case of zinc dust. Still another approach has been to prepare colloidal solutions of sodium silicate, exchange lithium for the sodium to produce a lithium silicate colloidal solution, and then add zinc powder as a sacrificial anode to the colloidal solution. These coatings have been termed lithium polysilicate paints. However, these paints are fairly expensive to produce and require fillers to provide the desired opacity or density in the coating.
U.S. Pat. No. 3,678,144 teaches a process for producing porous and non-porous glass articles having a substantial range of oxide compositions by dissolving metal oxides characterized by M.sub.x O.sub.y in a true or colloidal aqueous solution of soluble silicates and certain organic compounds or inorganic salts, this solution having a pH greater than 10, and thereafter heating the solution to polymerize the silica, coprecipitate the added metal oxide therewith, and form a solid body.